Vanishing fine structure splittings in telecom wavelength quantum dots grown on (111)A surfaces by droplet epitaxy

TL;DR

This paper reports the growth of highly symmetric telecom-wavelength quantum dots with minimal fine-structure splitting, suitable for entangled photon sources in quantum communication.

Contribution

It demonstrates the fabrication of symmetric InAs/InAlAs quantum dots on (111)A surfaces with ultra-small fine-structure splittings at telecom wavelengths, advancing quantum dot applications.

Findings

Quantum dots emit across O, C, and L telecom bands.

Fine-structure splittings are significantly smaller than previous reports.

Presence of degenerate exciton lines confirmed by optical orientation.

Abstract

The emission cascade of a single quantum dot is a promising source of entangled photons. A prerequisite for this source is the use of a symmetric dot analogous to an atom in a vacuum, but the simultaneous achievement of structural symmetry and emission in a telecom band poses a challenge. Here we report the growth and characterization of highly symmetric InAs/InAlAs quantum dots self-assembled on C3v symmetric InP(111)A. The broad emission spectra cover the O (1.3 micron-m), C (1.55 micron-m), and L (1.6 micron-m) telecom bands. The distribution of the fine-structure splittings is considerably smaller than those reported in previous works on dots at similar wavelengths. The presence of dots with degenerate exciton lines is further confirmed by the optical orientation technique. Thus, our dot systems are expected to serve as efficient entangled photon emitters for long-distance fiber-based quantum key distribution.